Telecommunications networks deliver data by routing data units, such as Asynchronous Transfer Mode ("ATM") cells, from source to destination through switches. Each switch includes input/output ("I/O") ports through which the ATM cells are received and transmitted. The switch determines the appropriate port for output transmission of the cell based on the cell header, which contains destination indicating information.
Depending on the destination indicated in the cell header, it may be desirable to transmit the cell from multiple ports on the switch. Cells which enter a switch through one port and exit through one port are referred to as unicast cells. Cells which enter the switch through a single port and exit through multiple ports are known as multicast cells. While most existing switches are configured to handle unicast cells, not all switches are capable of multicast operation. Further, while most if not all multicast switches are capable of "spatial" multicast operation (transmission of single copies of a cell through multiple output ports), not all multicast switches are capable of "logical" multicast operation (transmission of multiple copies of a cell through a single output port), Logical multicast switches are known, but are more complex and costly than typical spatial-only multicast switches. Accordingly, it would be desirable to be able to handle logical multicast operation without significantly adding to the cost or complexity of the switch. Additionally, it would be useful to provide multicast type capability in switches which do not support multicast operation by design.